leetcode 177

第N高的薪水

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
declare T int default 0; 
SET T = N-1;
  RETURN (
      # Write your MySQL query statement below.
      select ifnull((select distinct salary from Employee order by salary desc limit T,1), null) as getNthHighestSalary
  );
END

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